Methimazole & Quality of life?

What would happen if I take my 15 year old cat off methimazole?  He was diagnosed with hyperthyroidism in October.  He has been taking methimazole tablets for five months.  Coincidentally, or not, his health has rapidly declined.  He started loosing fur around his neck, under his chin, on his abdomen and shins.  He also started forming scabs around his claws, that irritate his paw pads and make them swell.  And his weight loss is extreme.  He has gone from 12 lbs to 5 lbs in 5 months.  This time last year he was 18 lbs.

I've had complete blood work, UA's and the works done on him 3 times by 3 different vets.  There is no indication of any other health issue, and his thyroid levels are normal.  He is eating well, and drinking water, yet he is dehydrated and has lost so much weight that his body is attacking his muscles.  

I know I'm dealing with end of life care now. What would happen if I take him off the methimazole?  

Thanks for your input.  I look forward to hearing what the community has to say.

[opus88]

Oh I am so sorry for you and your dear baby, its so darn hard to watch them slowly decline before your eyes, I know I've been there too.
I can't answer your question, I don't think it would hurt personally, it seems perhaps he could have some sort of allergy to the pills?...or is the decline coincidental? hard to say...I would suggest you post this question on the ASK AN EXPERT FORUM...and a Vet will give you an answer.
Click on Pets in the top bar or just go to the lower right of this screen see Expert Related Forums...and click on one of the topics...such as 'geriatric pets'
Have you not asked your own Vet about this?....a quick phone call to them and you would know, I'm surprised one didn't advise you to try this already???
please let us know what you decide to do and how kitty is doing, again my best to you both...love and hugs